A form-based service is one in which the flow of data between service and user is described by a sequence of query/response interactions, or forms. Mawl is a domain-specific language for programming form-based services in a device-independent manner. We focus on Mawl's form abstraction, which is the means for separating service logic from user interface description, and show how this simple abstraction addresses seven issues in service creation, analysis, and maintenance: compile-time guarantees, implementation flexibility, rapid prototyping, testing and validation, support for multiple devices, composition of services, and usage analysis.